Cushioned-stroke reciprocatory hydraulic motor



June 23, 1964 R. E. WALKER 3,138,066

cusHoNED-STROKE RECIPROCATORY HYDRAULIC MOTOR Filed oct. 27, 1961 UnitedStates Patent O 3,138,066 CUSHIONED-STRGKE RECIPROCATORY HYDRAULHC MQTRRonald E. Walker, Riverside, Ontario, Canada, assignor to Phil WoodIndustries, Ltd., Windsor, Ontario, Canada, a corporation of CanadaFiled Get. 27, 1961, Ser. No. 148,264 3 Claims. (Cl. 91-25) Thisinvention relates to hydraulic motors and, in particular, toreciprocatory motors.

One object of this invention is to provide a reciprocatory hydraulicmotor having a cushioning arrangement for retarding the speed of travelof the motor piston near either or both ends of its stroke, so as toeliminate the shock otherwise occurring at either or both ends of thestroke thereof.

Another object is to provide a cushioned-stroke reciprocatory hydraulicmotor of the foregoing character wherein the retardation action isbrought about by gradually restricting the discharge from the cylinderas the piston nears the end of its stroke, thereby effecting a gradualslowing down of the speed of the piston as it nears the end of itsstroke.

Another object is to provide a cushioned-stroke reciprocatory hydraulicmotor, as set forth in the preceding objects wherein the restricteddischarge of fluid from the cylinder near the end of the piston strokeis brought by the provision of a plurality of bidirectional uid flowports arranged in sequence such that the piston during its travel willcover up these ports sequentially and thereby restrict the discharge offluid from the cylinder in response to its own travel near the end ofits stroke.

Another object is to provide a cushioned-stroke reciprocatory hydraulicmotor, as set forth in the preceding object, wherein free discharge flowof hydraulic fluid is provided during the intermediate portions of thestroke of the piston away from either or both ends of the stroke, sothat the mechanism operated by the hydraulic motor is actuated in arapid and efficient manner throughout the major part of its stroke.

The figure shows a cushioned-stroke reciprocatory hydraulic motor withthe upper half in central vertical section and the lower half mainly inside elevation, according to one `form'of the invention.

Referring to the drawing in detail, the gure shows a cushioned-strokereciprocatory hydraulic motor, generally designated 10, according to oneform of the invention as consisting generally of an elongated hydrauliccylinder 12 within which is reciprocably mounted a hydraulic piston 14,the stroke of which is cushioned near its opposite ends bystroke-cushioning devices, generally desig nated 16 and 18, of similarconstruction but oppositelydirected and therefore designated in detailwith similar reference numerals. The cylinder 12 consists of anelongated tubular barrel portion 20 having an annularly-grooved cylinderhead 22 welded to one end thereof in closing relationship therew-ith andwith an annularly-rabbeted attachment ring 24 welded to its opposite endand provided with axially-directed circumferentially-Spaced threadedholes 26.

Secured as by bolts or cap screws 28 to the attachment ring 24 of thecylinder 12 is a detachable cylinder head 30 provided withcircumferentially-spaced holes 32 aligned with the threaded holes 26 forthe passage of the cap screws 28. The attachment ring 24 and cylinderhead 30 are suitably rabbeted or grooved to receive sealing gaskets orO-rings 34 and 36 in order to prevent leakage of hydraulic fluid duringthe operation of the motor 10. The detachable cylinder head 30 isprovided with a central axial bore 38 terminating at its outer end in acounterbore 40 separated therefrom by an annular shoulder 42.

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Seated in the bore 38 and flanged to engage the annular shoulder 42 is aflanged piston rod bearing bushing 44 receiving sliding engagement ofthe piston rod 46 upon the reduced diameter portion 48 of which thepiston head 50 of the piston 14 is mounted. In order to prevent leakagearound the piston rod 46, a suitable packing 52 is provided in thecounterbore 40 and adapted to be compressed by the annular gland 54 bymeans of the bolts 58 extending therethrough and threaded into thecylinder head 30.

The reduced diameter inner endportion 48 of the piston rod 46 isthreaded to receive the retaining nut 60 by which the piston head 50 isheld securely on the piston rod portion 48 against the annular shoulder62 between it and the piston rod 46. The piston head 50 is grooved as at64 to receive piston rings 66 for preventing leakage between the pistonhead 50 and the cylinder bore 68 within the cylinder barrel 20. Theouter or external end of the piston rod 46 is provided with paralleltransverse bores 70 adapted to receive transverse bolts 72 securingthereto a cup-shaped coupling member 74 drilled in alignment with theholes 70. The coupling member 74 in turn carries a transverseapproximately cylindrical portion 76 bored transversely to receive abearing bushing 78 which in turn pivotally engages a pivot pin (notshown) by which the piston rod 46 is operatively connected to the dumptruck body or other load being moved.

Each stroke-cushioning device 16 or 18 includes a plurality ofbidirectional fluid flow discharge ports 80, 82, 84, 86 and 88 which arepreferably graduated in Width and arranged in sequence inlongitudinally-spaced relationship along the cylinder barrel 20 near theoppoiste ends thereof and adapted to be successively covered by thepiston head 50 as it nears each end of its stroke. Thus, the rst port 80to be covered as the piston head 50 nears the end of its stroke ispreferably wider than the remaining ports 82 to 88 inclusive so as t0 beof greater crosssectional area for the purpose of graduating thedischarge of hydraulic fluid. The term bidirectional uid flow is usedherein to mean permitting two-way ow of fluid through the ports 80 to88, i.e. in opposite directions, in contradistinction to theunidirectional or one-way flow permitted through the ports 122 and 124controlled by the unidirectional check valves 126 and 128 respectively.

Each set of ports 80 to 88 is covered by a valve casing having a radialend wall 92 Welded to the cylinder barrel 20 near its junction with thecylinder head 22 and an axial side wall 94 welded to the end wall 92 andto the cylinder barrel 20. The open end 96 of the valve casing 90 isclosed by a closure member 98 having a longitudinal bore 100 thereinopening intoy a chamber 102 adjacent the discharge ports 80 to 88 andclosed at its outer end by a threaded plug 104. Intermediate itsopposite ends the closure member 98 is provided with a transversethreaded service port 106 for the cushioning device 16 and 108 for thecushioning device 18.

The closure member 98 is provided near the outer end of each bore 100with a transverse threaded check valve bore 110 into which is threaded atubular ball check valve seat 112 against which a check valve ball 114is urged by a compression spring 116, the outer end of which is seatedagainst a screw plug 118 threaded into a couterbore 120 coaxial with thebore 110. These ports collectively constitute the check valves 126 and128 in the stroke cushioning devices 16 and 18. The cylinder barrel 20adjacent each of the cushion devices 16 and 18 is provided with a radialport 122 or 124 registering with the bore 110 of its respective checkvalve 126 or 128, as the case may be.

' In the operation of the invention, let it be assumed that the threadedports 106 and 108 are connected to pipes leading to a conventionalfour-way control valve (not shown) and thence respectively to ahydraulic pump or other suitable source of hydraulic pressure uid (notshown) and a hydraulic fluid reservoir (not shown). Assuming the partsto be in the positions shown in the drawing, with the piston 14 fullyretracted within the cylinder 12, to move the piston 14 outwardy andperform a working stroke, hydraulic pressure fluid is admitted to theservice port 106 while the service port 108 is connected to dischargefluid into a suitable reservoir (not shown) by way of the four-Wayvalve. Such reciprocatory hydraulic motor control circuits arewell-known among those skilled in the hydraulics art and are beyond thescope of the present invention.

The hydraulic pressure iluid entering the service port 106 presses theball 114 of the ball check valve 126 downward against its seat 112 andthereby prevents passage of any such fluid through the cylinder barrelport 122 into the cylinder bore 68 beyond the piston head 50.Accordingly, the hydraulic pressure uid ows iirst through the port 88 ofthe cushioning device 16, and acts against the piston head 50 to push itto the right, thereby successively uncovering the remaining ports 86,84, 82 and 80. With the enhanced flow of hydraulic pressure fluid intothe left-hand endl of the cylinder 12, the piston 14 gathers speed andperforms the work intended for it while moving toward the detachablecylinder head 30.

Meanwhile, the hydraulic fluid behind or to the right of the piston head50 is forced outward from that portion of the cylinder bore 68 to theright of the piston head 50 not only by passing out through the ports 80to 88 of the cushioning device 18 and thence through the bore 100 andservice port 108 to the reservoir but also through the port 124 andtubular valve seat 112 of the check valve 128, 4forcing the ball 114thereof o its seat against the thrust of its respective spring 116,thereby additionally permitting fluid to ow through the left-hand end ofthe bore 100 into the service port 108 and thence back into thereservoir.

As the piston head 50 of the piston rod 14 nears the right-hand end ofits stroke, it first covers the cylinder barrel port 124 and thensuccessively covers the discharge ports 80, 82, 84, 86 and 88 of thecushioning device 18. The consequent gradual cutting olf of dischargeilow of hydraulic uid by thus reducing the available discharge port areareduces the speed of the piston head 50 until it has substantiallyhalted as it reaches the right-hand end of its stroke. Meanwhile, theuncovering of the cylinder port 124 by the travel of the piston head 50to the right permits a portion of the pressure fluid to escape throughthe port 122 and tubular valve seat 112 of the check valve 128 afterforcing the ball 114 thereof off its seat against the thrust of thespring 116, releasing this fluid also through the service port 108.

Reversal of the four-way valve (not shown) converts the service port 108into a hydraulic pressure fluid supply port and the service port 106into a hydraulic uid discharge port, reversing the foregoing operation.As a result, pressure fluid is admitted through the service port 108,bore 100 and sequential ports 80 to 88 of the cushioning device 18 whilehydraulic fluid is being discharged from the left-hand end of thecylinder 12 through the ports 80 to 88 of the cushioning device 16 andthence through the service port 106, as well as through the port 122 andtubular valve seat 112, forcing the check valve ball 114 of the checkvalve 126 temporarily olf its seat to permit such flow. As the piston 50moves to the left and reaches the ports 122 and 80 to 88 of thecushioning device 16, it successively covers them and, in the mannerdescribed above, gradually reduces the discharge flow and consequentlyreduces the speed of travel of the piston head 15 to the left, with theresult that shock at the end of the stroke is substantially eliminated.

Also in the manner described above, the piston 50 again uncovers thecheck valve port 122 of the check valve 126 as it passes by, againpermitting bypassing of the pressure lluid through the check valve andservice port 106 to the hydraulic iluid reservoir in the mannerdescribed above as occurring during the stroke of the piston 14 in theopposite direction.

What I claim is: l. A cushioned-stroke reciprocatory hydraulic motor,comprising a cylinder having a tubular cylinder barrel with a cylinderbore therein. a piston reciprocably mounted in said cylinder barrel,said piston including a piston rod and a piston head on said piston rodengageable with said cylinder bore, means for admitting hydraulicpressure fluid to said cylinder on one side of said piston head to movesaid piston along said cylinder, and means disposed near one end of saidcylinder barrel for gradually releasing hydraulic fluid from saidcylinder barrel on the opposite side of said piston head, saidfluid-releasing means including a first series of bidirectional uid owoutlet ports in said cylinder barrel arranged in axially-spacedlongitudinally-disposed relationship in said cylinder barrel and closedsequentially by said piston head in response to the travel of saidpiston head along said cylinder bore in one direction. saidfluid-releasing means also including a unidirectional uid release valvedisposed near said cylinder fluid outlet ports and opening outwardlyfrom said cylinder barrel into said cylinder bore in bypassingrelationship to said outlet ports. 2. A cushioned-stroke reciprocatoryhydraulic motor, comprising a cylinder having a tubular cylinder barrelwith a cylinder bore therein, a piston reciprocably mounted in saidcylinder barrel, said piston including a piston rod and a piston head onsaid piston rod engageable with said cylinder bore, means for admittinghydraulic pressure iiuid to said cylinder on one side of said pistonhead to move said piston along said cylinder, and means disposed nearone end of said cylinder barrel for gradually releasing hydraulic lluidfrom said cylinder barrel on the opposite side of said piston head, said`fluid-releasing means including a first series of bidirectional fluidow outlet ports in said cylinder barrel arranged in axially-spacedlongitudinally-disposed relationship to said cylinder barrel and closedsequentially by said piston head in response to the travel of saidpiston head along said cylinder bore in one direction, saidfluid-releasing means also being disposed near the opposite end of saidcylinder barrel and including a second series of bidirectional lluidflow outlet ports in said cylinder barrel also arranged inaxially-spaced longitudinally-disposed relationship in said cylinderbarrel but disposed remote from said first series of ports and alsoclosed sequentially by said piston head in response to the travel ofsaid piston head along said cylinder bore in the opposite direction tosaid one direction, said duid-releasing means also including aundirectional fluid release valve disposed near the opposite ends ofsaid cylinder near the first and second series of said fluid outletports and opening outwardly from said cylinder barrel into said cylinderbore in bypassing relationship to said outlet ports. 3. Acushioned-stroke reciprocatory hydraulic motor, comprising a cylinderhaving a tubular cylinder barrel with a cylinder bore therein, a pistonreciprocably mounted in said cylinder barrel, said piston including apiston rod and a piston head on said piston rod engageable with saidcylinder bore, means for admitting hydraulic pressure fluid to saidcylinder on one side of said piston head to move said piston along saidcylinder, and means disposed near one end of said cylinder barrel forgradually releasing hydraulic uid from said cylinder barrel on theopposite side of said piston head, said duid-releasing means including arst series of bidirectional Huid ow outlet ports in said cylinder barrelarranged in axially-spaced longitudinally-disposed relationship in saidcylinder barrel and closed sequentially by said piston head in responseto the travel of said piston head along said cylinder bore in onedirection, a valve casing with a chamber therein being secured to saidcylinder barrel near said one end of said cylinder with said outletports opening into said chamber,

said fluid-releasing means also including a unidirectional tluid releasevalve disposed near said valve casing and opening outwardly from saidcylinder barrel into said cylinder bore in bypassing relationship tosaid outlet ports.

References Cited in the file of this patent UNITED STATES PATENTSJohnson July 28, 1896 Aikens Feb. 14, 1928 Griffin Nov. 20, 1928 BlackSept. 1, 1931 Day Feb. 18, 1941 Cannon June 17, 1941 Geiger et al Junel5, 1948 Craig Aug. 15, 1950 Fox etal Oct. 22A 1957

1. A CUSHIONED-STROKE RECIPROCATORY HYDRAULIC MOTOR, COMPRISING ACYLINDER HAVING A TUBULAR CYLINDER BARREL WITH A CYLINDER BORE THEREIN.A PISTON RECIPROCABLY MOUNTED IN SAID CYLINDER BARREL, SAID PISTONINCLUDING A PISTON ROD AND A PISTON HEAD ON SAID PISTON ROD ENGAGEABLEWITH SAID CYLINDER BORE, MEANS FOR ADMITTING HYDRAULIC PRESSURE FLUID TOSAID CYLINDER ON ONE SIDE OF SAID PISTON HEAD TO MOVE SAID PISTON ALONGSAID CYLINDER, AND MEANS DISPOSED NEAR ONE END OF SAID CYLINDER BARRELFOR GRADUALLY RELEASING HYDRAULIC FLUID FROM SAID CYLINDER BARREL ON THEOPPOSITE SIDE OF SAID PISTON HEAD, SAID FLUID-RELEASING MEANS INCLUDINGA FIRST SERIES OF BIDIRECTIONAL FLUID FLOW OUTLET PORTS IN SAID CYLINDERBARREL ARRANGED IN AXIALLY-SPACED LONGITUDINALLY-DISPOSED RELATIONSHIPIN SAID CYLINDER BARREL AND CLOSED SEQUENTIALLY BY SAID PISTON HEAD INRESPONSE TO THE TRAVEL OF SAID PISTON HEAD ALONG SAID CYLINDER BORE INONE DIRECTION. SAID FLUID-RELEASING MEANS ALSO INCLUDING AUNIDIRECTIONAL FLUID RELEASE VALVE DISPOSED NEAR SAID CYLINDER FLUIDOUTLET PORTS AND OPENING OUTWARDLY FROM SAID CYLINDER BARREL INTO SAIDCYLINDER BORE IN BYPASSING RELATIONSHIP TO SAID OUTLET PORTS.